Question

我目前正在制作iOS应用程序将Objective-C。我有很多if语句使UIImageView出现在我的应用程序中。有没有更有效的方法来做，或者我应该保留所有的if语句？

由于

编辑请参阅以下代码：

if (obscacle.center.x < 0) {
    randomPosition = arc4random() %20;
    randomPosition = randomPosition + 110;
    obscacle.center = CGPointMake(568, randomPosition);
}

if (obscacle2.center.x < 0) {
    randomPosition = arc4random() %20;
    randomPosition = randomPosition + 110;
    obscacle2.center = CGPointMake(568, randomPosition);
}


if (top1.center.x < -50) {
    randomPosition = arc4random() %20;
    top1.center = CGPointMake(550, randomPosition);
    randomPosition = randomPosition + 265;
    bottom1.center = CGPointMake(568, randomPosition);
}

if (top2.center.x < -50) {
    randomPosition = arc4random() %20;
    top2.center = CGPointMake(550, randomPosition);
    randomPosition = randomPosition + 265;
    bottom2.center = CGPointMake(568, randomPosition);
}

if (top3.center.x < -55) {
    randomPosition = arc4random() %20;
    top3.center = CGPointMake(550, randomPosition);
    randomPosition = randomPosition + 265;
    bottom3.center = CGPointMake(568, randomPosition);
}

if (top3.center.x < -55) {
    randomPosition = arc4random() %20;
    top3.center = CGPointMake(550, randomPosition);
    randomPosition = randomPosition + 265;
    bottom3.center = CGPointMake(568, randomPosition);
}

if (top4.center.x < -55) {
    randomPosition = arc4random() %20;
    top4.center = CGPointMake(550, randomPosition);
    randomPosition = randomPosition + 265;
    bottom4.center = CGPointMake(568, randomPosition);
}

if (top5.center.x < -55) {
    randomPosition = arc4random() %20;
    top5.center = CGPointMake(550, randomPosition);
    randomPosition = randomPosition + 265;
    bottom5.center = CGPointMake(568, randomPosition);
}

if (top6.center.x < -55) {
    randomPosition = arc4random() %20;
    top6.center = CGPointMake(550, randomPosition);
    randomPosition = randomPosition + 265;
    bottom6.center = CGPointMake(568, randomPosition);
}

if (top7.center.x < -55) {
    randomPosition = arc4random() %20;
    top7.center = CGPointMake(568, randomPosition);
    randomPosition = randomPosition + 265;
    bottom7.center = CGPointMake(568, randomPosition);
}

Answer 1

看起来你需要一些for循环。

伪代码：

for each obstacle in [array of obstacles]:
    if (obscacle.center.x < 0):
        randomPosition = arc4random() %20
        randomPosition = randomPosition + 110
        obscacle.center = CGPointMake(568, randomPosition)

同样适用于“顶级”。

请注意，这与效率无关，而是使代码更整洁，更易于维护。在性能方面，任何一种方法都应该超出您的使用范围。

Answer 2

很难说没有看到你的代码，但由于某些原因，有时候switch语句是更好的替代。

示例：

switch (expression)
 {
     case match1:
          statements
          break;

     case match2:
          statements
          break;

     default:
          statements
          break;
 }

所有这些都取决于你想要做什么。

Answer 3

根据您尝试做的事情，您可以完全消除if语句。

您说您正在使用if来选择要显示的图像。因此，如果您根据您在if中测试的变量命名图像，则可以改为使用该变量来选择正确的名称。

比使用If语句更高效的代码

3 个答案: